Enhancement - Subst object

- Implemented most of Subst object, except Subst::apply

src/sandbox/T.h

@@ -42,6 +42,12 @@ public:
   std::string composeCSV ();
 
   // TODO Series of helper functions.
+/*
+  status getStatus () const;
+  void setStatus (status s);
+*/
+
+  bool validate () const;
 
 private:
 };